Anorectal disorders including constipation and fecal incontinence are common, embarrassing, and sometimes disabling gastrointestinal (GI) complaints. Constipation can involve a variety of symptoms such as excessive straining, hard stools, feeling of incomplete evacuation, use of digital maneuvers, and infrequent defecation. Fecal incontinence is defined as the unintentional loss of solid or liquid stool. Chronic constipation is one of the most common GI complaints of patients, being reported in 10 to 15% of the adult population in the United States. Fecal incontinence is also common, being reported in 6 to 10% of the adult population in the United States. The prevalence of both conditions appears to be greater in females and increases with age. In addition, both chronic constipation and fecal incontinence are often attended by decreased quality of life, decreased work productivity, and increased health care costs.
Chronic constipation may be divided into two main physiological subgroups: slow-transit constipation (colonic inertia) and dyssynergic defecation. Some patients (e.g., patients with irritable bowel syndrome) may exhibit features of both of these types of chronic constipation. Patients with slow-transit constipation may exhibit impaired phasic colonic motor activity, diminished gastrocolonic responses after a meal, abnormal colonic motor activity upon waking, and underlying neuropathy as demonstrated by a paucity of interstitial cells of Cajal (ICC). Patients with dyssynergic defecation may exhibit abnormal coordination of abdominal, rectoanal, and pelvic floor muscles when attempting to defecate, as well as impaired rectal sensation.
Available laxative therapies are primarily aimed at improving colon transit and secretion, and offer only limited efficacy to patients with dyssynergic defecation. For dyssynergic defecation, biofeedback training has been shown to be far superior to laxative therapy. Unfortunately, current tools for diagnosing dyssynergic defecation are not widely available, require dedicated infrastructure, are expensive, rely on limited data/measurements, and/or involve complicated data analysis. One tool that suffers from these deficiencies, despite being widely considered as the current “gold standard” for diagnosing dyssynergic defecation, is the anorectal manometry (ARM) system. ARM systems, which are catheter-based systems that monitor the anal sphincter to assess abnormal contractions, are often not accessible. Even when available, ARM systems are cost-prohibitive for many patients and health care providers.
Given the expense of accurately diagnosing dyssynergic defecation, primary care physicians and most GI specialists simply prescribe a laxative and suggest dietary restrictions to patients complaining of symptoms indicative of constipation (excessive straining, hard stools, etc.). Primary care physicians may only refer a patient to a GI specialist with proper diagnostic tools, and GI specialists may only utilize those tools, after such therapies have been proven ineffective. By that time, however, the patient may have incurred a significant amount of health care costs, and the patient's symptoms may have intensified. Further, the patient is then subject to the considerable expense associated with using current diagnostic tools (e.g., the ARM system) before receiving biofeedback or other therapies that are most appropriate for the specific condition of the patient. Thus, the lack of an accurate, lower-cost diagnostic tool for health service providers can lead to additional cost, time, and suffering for patients.
Fecal incontinence can arise as a consequence of nerve or muscle damage involving the pelvic floor and/or anal sphincter. A variety of other factors, including obesity, physical inactivity, genetic factors, comorbid diseases which affect neuromuscular function or cause diarrhea, and previous trauma, have been associated with fecal incontinence. Assessment of the pelvic floor and anal sphincter muscles is critical to the evaluation of patients with fecal incontinence. Discovery of reduced anal sphincter pressure at rest or when attempting to voluntarily squeeze the anal sphincter muscle can identify patients who might benefit from physical therapy and biofeedback aimed at strengthening the anal sphincter and pelvic floor muscles. While some of this information can be gleaned from a detailed digital rectal examination, as with dyssynergic defecation most primary care physicians and GI specialists are not properly trained to perform this type of evaluation. Even when a provider is trained to perform a detailed digital rectal examination, findings in patients with fecal incontinence are often subtle and difficult to definitively identify without the use of more quantitative testing with anorectal manometry. Unfortunately, all of the issues involving accessibility, infrastructure, and cost that are problematic for using anorectal manometry to identify dyssynergic defecation are also operative in the evaluation of patients with fecal incontinence.